Forty adult patients undergoing elective surgical procedures requiring cardiopulmonary bypass will be studied in the perioperative period including the 24 hours immediately following operation. The hypotheses to be tested are: 1) measures of extravascular lung water and colloid osmotic pressure can be used to predict the postoperative clinical respiratory status of patients; and 2) the use of a colloid rather than a crystalloid solution for perioperative fluid resuscitation affects postoperative respiratory function and the need for respiratory support, hemodynamic variables, and cost. Possible adverse effects associated with either fluid resuscitation regimen will be determined.